Return The Filename For A Database Connection

const char *sqlite3_db_filename(sqlite3 *db, const char *zDbName);

R-41554-07046:[The sqlite3_db_filename(D,N) interface returns a pointer to a filename
associated with database N of connection D.]R-53691-30751:[The main database file
has the name "main".]
If there is no attached database N on the database
connection D, or if database N is a temporary or in-memory database, then
a NULL pointer is returned.

R-41640-10889:[The filename returned by this function is the output of the
xFullPathname method of the VFS.]R-42868-39706:[In other words, the filename
will be an absolute pathname, even if the filename used
to open the database originally was a URI or relative pathname.]